Preheat oven to 325 degrees F and spray a 9" loaf pan generously with cooking spray or line with parchment paper.

Cream together the butter and sugar until light and fluffy. Stir in eggs one at a time until well combined.

In a separate bowl, mash the bananas with a fork. Stir in milk. Add the banana mixture to the butter mixture and stir until combined.

In another bowl, sift together the flour, baking soda, baking powder and salt. Add the dry mixture to the wet mixture and still just until combined - do not overmix.

Gently fold in chocolate chips and walnuts.

Pour batter into the prepared loaf pan. Bake for 1 hour or until golden brown and a toothpick inserted into the center comes out clean.

Cool in the pan for half an hour before removing and transferring to a wire rack to cool completely.